The present invention generally relates to a battery monitor for testing a plurality of battery conditions at periodic intervals The present invention more particularily relates to a battery monitor for use in a system of the type including a battery as an auxiliary power source and a power supply for providing the primary source of power for the system and for maintaining a charge on the battery. The battery monitor tests for theft of the battery, whether the battery voltage is at least equal to some nominal voltage, and whether the battery discharge rate is greater than a preselected rate.
There are many systems which utilize batteries as primary or auxiliary sources of power. In such systems, it is desirable that the battery or batteries be checked at periodic intervals to confirm that the batteries will perform properly if called upon for delivering power.
One such system, wherein battery monitoring is preferrable is in a fire detection and security alarm system. In systems of this type, it is customary to utilize a power supply which converts AC line current to direct current for providing the primary source of power for the system and to incorporate a battery or batteries which are available as an auxiliary or back-up power source. To insure that the battery or batteries are able to provide sufficient power if called upon, battery monitoring circuits are employed. These circuits test the battery or batteries to determine whether the voltage output of the auxiliary power source is at least equal to some nominal voltage under a preselected load condition.
While such battery monitors have been adequate for the purpose, there remains room for improvement. For example, theft of batteries is not uncommon in security systems. Unfortunately, prior art monitors have provided just one indication whether the battery voltage is normal or low. In such monitors, both a low battery voltage condition and the absence of a battery, due to theft for example, would result in the same indication namely, a low battery voltage indication. Hence, if a low battery voltage indication is present, there is no way of knowing whether the batteries are merely low in charge or whether the batteries are missing altogether.
In addition, the longevity of a battery under load is an important consideration. Monitors of the prior art do not provide for such a measurement. Longeveity is important because if the batteries are to take over the responsibilities of delivering power to the security system, it is helpful to know that the batteries are capable of providing sufficient current under load for some minimum length of time, which is long enough to assure that the AC power will return before the batteries are exhausted. If the batteries fail before AC power is restored, the system will not be functional for a time, leaving the premises to be protected, unprotected.
A further drawback of prior art battery monitors is that they lack flexibility. Such a lack of flexibility renders it impossible to adapt a monitor for a specific application because test parameters, such as voltage test levels, are not readily alterable.
It is therefore a general object of the present invention to provide a new and improved battery monitor for testing the condition of a battery supply at periodic intervals.
It is a more specific object of the present invention to provide a battery monitor which tests for and provides a separate indication of theft of the batteries.
It is a more specific object of the present invention to provide such a battery monitor which further provides a separate test for nominal voltage and a separate indication when the voltage of the batteries is below a nominal voltage.
It is a still further object of the present invention to provide a battery monitor which additionally tests for the discharge rate of the battery and which provides a separate indication when the quality of the batteries is low, because the discharge rate of the batteries exceeds a preselected discharge rate.
It is a still further object of the present invention to provide a battery monitor wherein the test parameters are readily alterable to enable the battery monitor to be adapted for use in a wide variety of applications.